OBJECTIVE. In light of the rapidly increasing frequency of pediatric CT examinations, the purpose of our study was to assess the lifetime cancer mortality risks attributable to radiation from pediatric CT.MATERIALS AND METHODS. Organ doses as a function of age-at-diagnosis were estimated for common CT examinations, and estimated attributable lifetime cancer mortality risks (per unit dose) for different organ sites were applied. Standard models that assume a linear extrapolation of risks from intermediate to low doses were applied. On the basis of current standard practice, the same exposures (milliampere-seconds) were assumed, independent of age.RESULTS. The larger doses and increased lifetime radiation risks in children produce a sharp increase, relative to adults, in estimated risk from CT. Estimated lifetime cancer mortality risks attributable to the radiation exposure from a CT in a 1-year-old are 0.18% (abdominal) and 0.07% (head)—an order of magnitude higher than for adults—although those figures st...

https://www.ajronline.org/doi/pdf/10.2214/ajr.176.2.1760289

Estimated Risks of Radiation-Induced Fatal Cancer from Pediatric CT

Assessment of fracture risk and its application to screening for postmenopausal osteoporos

The criteria required for an effective screening strategy for osteoporosis are largely met in Caucasian women. The disease is common and readily diagnosed by the measurement of bone mineral with single- or dual-energy absorptiometry. Such measurements have high specificity but lower sensitivity, so that the value of the technique is greater for those identified as being at higher risk. Against this background there is little evidence that osteoporosis can usefully be tackled by a public health policy to influence risk factors such as smoking, exercise and nutrition. This suggests that it is appropriate to consider targetting of treatment with agents affecting bone metabolism to susceptible individuals. Since the main benefits of the use of hormone replacement therapy (HRT) are probably on cardiovascular morbidity, the major role for selective screening is to direct non-HRT interventions. An appropriate time to consider screening and intervention is at the menopause, but screening at later ages is also worthy of consideration. Since the cost of screening is low and that of bone-active drugs is high, the selective use of screening techniques will improve the cost-benefit ratio of intervention.

Assessment of fracture risk and its application to screening for postmenopausal osteoporosis: synopsis of a WHO report. WHO Study Group.

Patterns of bone loss in the axial and the appendicular skeleton were studied in 185 normal volunteers (105 women and 82 men; age range, 20--89 yr) and in 76 women and 9 men with vertebral fractures due to osteoporosis. Bone mineral density was measured in vivo at the lumbar spine (predominantly trabecular bone) by dual photon absorptiometry and at the midradius (greater than 95% cortical bone) and distal radius (75% cortical and 25% trabecular bone) by single photon absorptiometry. In normal women, bone diminution from the vertebrae began in young adulthood and was linear. In the appendicular skeleton, bone diminution did not occur until age 50 yr, was accelerated from aged 51 to 65 yr, and then decelerated somewhat after age 65 yr. Overall bone diminution throughout life was 47% for the vertebrae, 30% for the midradius, and 39% for the distal radius. In normal men, vertebral and appendicular bone diminution with aging was minimal or insignificant. Mean bone mineral density was lower in patients with osteoporosis than in age- and sex-matched normal subjects at all three scanning sites, although spinal measurements discriminated best; however, there was considerable overlap. By age 65 yr, half of the normal women (and by age 85 yr, virtually all of them) had vertebral bone mineral density values below the 90th percentile of women with vertebral fractures and, thus, might be considered to have asymptomatic osteoporosis. For men, the degree of overlap was less. The data suggest that disproportionate loss of trabecular bone from the axial skeleton is a distinguishing characteristic of spinal osteoporosis.

/pdf/differential-changes-in-bone-mineral-density-of-the-2pguxhy5ed.pdf

Differential changes in bone mineral density of the appendicular and axial skeleton with aging: relationship to spinal osteoporosis.

Methods for the assessment of human body composition: traditional and new.

The mineral content of bone can be determined by measuring the absorption by bone of a monochromatic, low-energy photon beam which originates in a radioactive source (iodine-125 at 27.3 kev or americium 241 at 59.6 kev). The intensity of the beam transmitted by the bone is measured by counting with a scintillation detector. Since the photon source and detector are well collimated, errors resulting from scattered radiation are reduced. From measurements of the intensity of the transmitted beam, made at intervals across the bone, the total mineral content of the bone can be determined. The results are accurate and reproducible to within about 3 percent.

https://science.sciencemag.org/content/sci/142/3589/230.full.pdf

Measurement of Bone Mineral in vivo: An Improved Method

Bone mineral was determined using a radiologic absorptiometric method. The attenuation of a low-energy beam from a well-collimated radionuclide source (125I or 241Am) was measured using a collimated scintillation detectorpulse height analyzer system. The absorption of the photon beam by bone, as shown by this scanning method, was highly correlated with the weight of standard sections on excised bones (r = 0.97 to 0.99). Even scans on tissue covered cadaver forearms were highly correlated (r = 0.96) with the weight of underlying bone components and single scans on human ulnae were highly correlated (r= 0.96) with total ulna weight. The precision (2%) and accuracy (4 to 7%error) were the highest ever demonstrated for a radiologic method of bone determination and the large inaccuracies (more than 20 to 30% error) of older methods, which used photodensitometry of radiographs, were eliminated by the present method. Improved techniques allow even higher precision (1 to 2%) and accuracy (2 to 4%); therefore, the radionuclide absorption method is potentially useful for diagnostic, clinical and normative evaluation of appendicular skeletal mineralization where older photodensitometric methods cannot be used.

Precision and Accuracy of Bone Mineral Determination by Direct Photon Absorptiometry

The adverse effects of osteoarthritis on the quality of life for tens of millions of people and on the costs of health care and economic productivity make it a major health problem that will increase in incidence and impact with the aging of the population. Although in most patients the cause of osteoarthritis remains unknown and no cure has been identified, appropriate diagnosis and treatment, including education of the patients, can minimize symptoms and help patients maintain active and productive lives. Accomplishing this aim requires that physicians have an understanding of the pathophysiology of joint degeneration and the relationships between joint degeneration and the clinical syndrome of osteoarthritis. Although much remains to be learned about the development and progression of the joint degeneration responsible for osteoarthritis, it is clear that the loss of articular cartilage results from disruption of the structural integrity of the articular cartilage coupled with or caused by an imbalance in the anabolic and catabolic activity of the tissue. The progression of joint degeneration varies considerably among patients. In some individuals the joint degenerates rapidly; in others the degenerative changes progress slowly over decades and in others the disease may remain stable. In rare patients, the joint degenerative changes spontaneously improve. Although joint degeneration is the underlying cause of the symptoms of osteoarthritis, including joint pain and loss of joint function, not all patients with joint degeneration have symptoms of osteoarthritis. Future therapeutic approaches may include disease-modifying drugs and surgical procedures that correct mechanical abnormalities, debride joints, and replace degenerated articular cartilage with implants that stimulate restoration of a cartilaginous joint surface. Development of methods to detect and monitor subtle changes in cartilage metabolism and identify the joint changes that precede loss of articular cartilage may make it possible to detect the earliest signs of osteoarthritis, when therapeutic interventions have the greatest potential for preventing progression of the disease.

A reliable in vivo measurement of bone-mineral content.

The mineral content of bone can be determined by measuring the absorption by bone of a monochromatic, low-energy photon beam which originates in a radioactive source (iodine-125 at 27.3 kev or americium-241 at 59.6 kev). The intensity of the beam transmitted by the bone is measured by counting with a scintillation detector. Since the photon source and detector are well collimated, errors resulting from scattered radiation are reduced. From measurements of the intensity of the transmitted beam, made at intervals across the bone, the total mineral content of the bone can be determined. The results are accurate and reproducible to within about 3 percent.

/pdf/measurement-of-bone-mineral-in-vivo-an-improved-method-2pf6najksu.pdf

Measurement of bone mineral in vivo: an improved method

The differential cross sections for elastic scattering of alpha-particles by ${\mathrm{O}}^{16}$ were measured in a gas-scattering chamber using alpha-particles accelerated in an electrostatic generator over the energy region from 0.94 to 4.0 Mev. Cross sections were measured at $\ensuremath{\theta}(\mathrm{cm})=168.0\ifmmode^\circ\else\textdegree\fi{}; 140.1\ifmmode^\circ\else\textdegree\fi{}; 124.6\ifmmode^\circ\else\textdegree\fi{}; \mathrm{and} 90.0\ifmmode^\circ\else\textdegree\fi{}$. Because both particles have zero spin the partial wave analysis is exceptionally simple and fixes unambiguously the angular momentum and parity of each level. The resonances were analyzed using the Wigner-Eisenbud one-level approximation to determine the width and resonant energy of each resonance. Five scattering anomalies were observed which correspond to excited states of ${\mathrm{Ne}}^{20}$ with the following energies, angular momenta, and parities: 6.738 Mev, $J={0}^{+}$; 7.182 Mev, $J={3}^{\ensuremath{-}}$; 7.218 Mev, $J={0}^{+}$; 7.450 Mev, $J={2}^{+}$; and 7.854 Mev, $J={2}^{+}$. The uncertainty in these energies is about 10 kev, most of which is due to the uncertainty of the energy loss in the gas. None of the levels have reduced widths greater than two percent of the single particle width.

John R. Cameron

Papers

Measurement of Bone Mineral in vivo: An Improved Method

Precision and Accuracy of Bone Mineral Determination by Direct Photon Absorptiometry

A reliable in vivo measurement of bone-mineral content.

Measurement of bone mineral in vivo: an improved method

Elastic Scattering of Alpha-Particles by Oxygen.